Physicians use a variety of prostheses to correct problems associated with the cardiovascular system, especially the heart. The ability to replace or repair diseased heart valves with prosthetic devices has provided surgeons with a method of treating heart valve deficiencies due to disease and congenital defects. One procedure involves removal of the native valve and surgical replacement with a prosthetic heart valve.
Prosthetic heart valves have leaflets or occluders that perform the function of opening and closing to regulate the blood flow through the heart valve. Typically, heart valve leaflets must either pivot or flex with each cycle of the heart to open and close the valve. Heart valves function as check valves, which open for flow in one direction and close in response to pressure differentials to limit reverse flow. Prostheses can be constructed from natural materials, synthetic materials or a combination thereof. Prostheses with rigid occluders generally include, for example, biocompatible metals, ceramics, carbonaceous solids, such as pyrolytic carbon, polymers and combinations thereof.
While prostheses with tissue leaflets are considered nonthrombogenic, mechanical heart valves with rigid occluders have the advantage of proven durability through decades of use. However, prostheses with rigid occluders are associated with potential blood clotting on or around the prosthetic valve and thromboembolism. Blood clotting can lead to acute or subacute dysfunction of the valve. For this reason, patients with mechanical heart valves remain on anticoagulants for as long as the valve remains implanted. Anticoagulants have associated risks and cannot be taken safely by certain individuals. Thus, there is an interest in providing mechanical heart valve prostheses with modified surface properties that can reduce thrombosis. Similar surface modification may be useful for other medical devices that contact body fluids.